Mass Spectral Characteristics of C 19 and C 20 Tricyclic Terpanes Detected in Latrobe Tasmanite Oil Shale

The saturated tricyclic terpane composition of the solvent-extractable hydrocarbon fraction of Latrobe Tasmanite oil shale has been investigated. A homologous series of the usual cheilanthane tricyclic terpanes, including several C₂₀–C₃₀ 13(H),14(H) stereoisomers, was detected, together with several novel C₁₉ and C₂₀ tricyclic terpanes. Classical and metastable daughter scan 70 eV mass spectra for six C₁₉ tricyclic terpanes and ten C₂₀ tricyclic terpanes are reported here, including a number of isomers for the first time. The mass spectral and gas chromatographic data distinguish the unknown tricyclic terpane isomers from previously characterised cheilanthanes, which have been widely reported from molecular studies of Tasmanite material. Several mass spectral trends are consistently observed between all detected tricyclic terpanes, suggesting a close cheilanthane-related structural affinity.